G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

Plastic- Sandwiging Steel Sheet
In this product, a plastic sheet is sandwiched between two steel sheets. A type recently supplied to one automo­bile maker, consisting of a 0,6-mm plastic sheet between two 0,2-mm steel sheets, is only half the weight of the usual 1-mm steel sheet and yet has the same rigidity. It is used for trunk-lid panels and air-cleaner covers.

A Wonder Metal
The story of titanium is extraordinary. To begin with, it was discovered twice. A British scientist, William Gregor found it first and called it menachanite, and six years later, in 1797, M. H. Klaproth, a German chemist, also found it and gave it its present name.

For many years, titanium was of inertest only to re­search chemists-it was considered too brittle to be of any practical value. Yet it was the impurities with which it was usually associated (it forms compounds easily with nearly every known element) that made it brittle.

It cost the chemists in many countries endless efforts to isolate pure titanium and even more to start producing it commercially. Today its output is very large.

Titanium has one surprising property — it is complete­ly inert in biological media, something the medical com­munity was quick to notice. It is being used to make artifi­cial joints and many other things necessary in surgery and Ortho­pedics. Titanium instruments do not corrode, and are thir­ty per cent lighter than instruments made of stainless steel.

Titanium's high standard of corrosion resistance, lightness, tensile strength, and the ease of forging, rolling and stamping are finding it more and more uses. Tita­nium alloys are very useful in mechanical engineering, and for chemical and refractory apparatus. Titanium helped Soviet design engineers to surmount the sound and heat barriers in supersonic and high-altitude aircraft designing. On earth, it shows good work at chemical plants, in the pulp-and-paper and food industries. More­over, it is still a source of surprise for the investigator produced a material that has a kind of "memory as the following experiment shows: a thin bent strip of the new alloy wall clamped to a stand, a 500-gram weight hung on the free end. A current was passed through for sever a seconds, which heated the strip to more than 100 L. As it commanded by an enigmatic force, it straightened out like a tight spring and lifted the load. When the current was switched off, the strip gradually went back to its original shape. The cycle was repeated a number of times and the strip always "remembered" its original shape.' The surprising phenomenon of direct conversion of ther­mal energy into mechanical is seen with the naked eye. The explanation is in the crystalline modifications of titanium-nickel alloy, which, changing with the tempera­ture, also changes back again.

This is why the material has a "memory" and special acoustic properties. At room temperature, the alloy called titanium nickelodeon becomes soft, ductile and does not pro-duce the characteristic metallic sound when struck. How­ever, when it is heated to a certain temperature, it becomes hard, resistant, and ringing.

There will undoubtedly be some unusual applications for this phenomenon in the future — even at this early stage it is clear that titanium nickelodeon-based alloys will be useful in many areas. For instance, in sensitive pickups which are activated by a change in temperature, in acoustics for sound absorption, etc., etc.

Titanium and its alloys are coming out in the com­mercial field — they have already made quite a name for themselves as structural materials.

Oersted
Nearly, a century and a half ago, a Danish physicist Oersted, was demonstrating current electricity to a class, using a copper wire, which was joined to a voltage cell. Amongst the apparatus on his demonstration table there happened to be a magnetic needle, and Oersted noticed that when the hand holding the wire moved near the needle, the latter was occasionally deflected. He imme­diately investigated the phenomenon systematically and found that the strongest deflection occurred when he held the wire horizontally and parallel to the needle. With a quick jump of imagination he then disconnected the ends of the wire and reconnected them to the opposite poles of the cell — thus reversing the current — and found that the needle was deflected in the opposite direction. This chance discovery of the relationship between electricity and magnetism not only led quickly to the invention of the electric dynamo and hence to the large scale utilization of electric energy, but forms the basis for modern electro­magnetic field theory, which is now an extremely valuable tool in both macro- and micro-physics.